The present invention relates to a fluorescent latent image transfer film, and a method for forming an fluorescent latent image by using this film, and more specifically to a fluorescent latent image transfer film making it possible to form any fluorescent latent image of any photograph, any pattern, any character or the like onto a transfer receiving material so as to form an image excellent in design and capability of preventing falsification; a method for transferring such a fluorescent latent image; and a security pattern formed matter having a fluorescent latent image.
In order to prevent forgery or falsification of a printed matter such as a document, a note or a card, there have hitherto been known means for forming a fluorescent latent image, which cannot be recognized through usual visible rays but emit fluorescence at the time of receiving ultraviolet rays so as to be recognized, into any pattern. In order to form this fluorescent latent image, there is usually used a method of printing the fluorescent latent image with a fluorescence developing ink.
Hitherto, as a simple printing method, a thermal transfer method has widely been used. This method makes it possible to form various images simply, so as to be used for the preparation of printed matters the print-number of which is a few, for example, cards such as an ID card.
A fluorescent latent image can be recorded onto a transfer receiving material, such as a card, by heating a thermal transfer film having a thermal transfer layer containing a fluorescent agent with a heating means such as a thermal head or a laser. The thermal transfer method includes sublimation type thermal transfer recording method and heat fusible type thermal recording method. In the sublimation type thermal transfer recording method, a sublimation dye is used and the dye is sublimated and transferred with the above-mentioned heating means. In the heat fusible thermal recording, there is used a heat fusible ink containing a colorant such as a pigment in a vehicle such as a wax, and ink in a heat fusible ink layer is softened with the heating means and the softened ink is transferred for recording.
In the heat fusible thermal recording, it is possible to form an image of a character, a number or the like easily and vividly. In the sublimation thermal transfer recording, gradiation-property is excellent, so that an image such as a facial photograph can be precisely and beautifully formed. The respective recording manners have such features.
Japanese Patent Application Laid-Open Nos. 2-106359, 6-316167, 7-223376, 7-117366 and the like disclose a sublimation thermal transfer film making it possible to record and form a fluorescent latent image having continuous gradation. These publications also describe various kinds of fluorescent compounds for forming a fluorescent latent image.
However, in the transfer film using the fluorescent compound described in the above-mentioned publications, and a method of using this transfer film to form a fluorescent latent image, there remains a problem that transferability of the fluorescent latent image and gradiation-property are not sufficient.
In the case that fluorescent ink is used to make a given pattern of the fluorescent ink by printing, the following problems arise.
(1) Since the fluorescent ink pattern is made by printing, a sufficient amount of the applied ink cannot be ensured. Thus, the degree of fluorescence color development is insufficient.
(2) If the amount of the applied ink is increased at the time of printing to obtain sufficient color development brightness, print reproduction of a minute pattern deteriorates. If the layer of the ink becomes thick, unevenness is generated in the raw matters subjected to printing-process. As a result, if the matters are long sheets, they may be subjected to blocking.
(3) In the case that the amount of a fluorescent pigment component is increased in a fluorescent pigment ink to raise the ratio of the fluorescent pigment to a binder resin which is a vehicle (abbreviated to the ratio of P/V hereinafter) and raise the luminescence intensity of a fluorescent latent image, accordingly, the print layer made of the ink whitens because of high concentration of the fluorescent pigment. Unfavorably, therefore, a portion where an image is printed with the fluorescent ink is easily recognized with eyes.
Japanese Patent application No. 4-319918 (Japanese Patent Application Laid-Open No. 6-166264) describes a method of using an ink containing an ultraviolet ray absorber to perform printing and forming on a sheet having a fluorescent latent image, thereby obtaining a fluorescent latent image having a specified pattern.
In this method, however, it is necessary to cause a support medium (a medium to be recorded) having a recording layer to contain a fluorescent material beforehand. For the formation of the pattern used the ultraviolet ray absorber, it is essential to use the special medium to be recorded which contains the fluorescent material. Thus, it is impossible to use plain paper to which such a processing is not applied. Therefore, the medium to be recorded is restrictive. This method cannot widely be used.
In the light of the above-mentioned problems in the prior art, an object of the present invention is to provide a fluorescent latent image transfer film making it possible to form a fluorescent latent image excellent in transferability and gradiation-property; a fluorescent latent image transfer method using the same; and a printed matter on which a fluorescent latent image is formed.
Another object of the present invention is to provide a security pattern formed matter making it possible to obtain sufficient brightness of a fluorescent latent image pattern, and recognize the fluorescent image easily without having a bad influence on the raw material of during printing-process.
In order to attain the above-mentioned objects, in the present invention there is provided a fluorescent latent image transfer film wherein a fluorescent ink layer formed of a resin binder comprising a fluorescent agent represented by the following formula (1) is formed on/above a heat-resistant substrate film. 
wherein R1 is 
(n is a positive integer),
and R2 and R3 each represents H or an alkyl group.
In the above described fluorescent latent image transfer film, the resin binder is composed mainly of a polyvinyl acetal resin, a polyvinyl butyral resin, or a mixture thereof.
In the fluorescent latent image transfer film, one or more layers selected from at least one of yellow, magenta, cyan and black thermal sublimation dye layers, and a heat fusible black ink layer are formed on and successively along a transfer face on which the fluorescent ink layer is formed.
In the fluorescent latent image transfer film, a protective layer is formed on and successively along the transfer face on which the fluorescent ink layer is formed.
In the fluorescent latent image transfer film, a thermal transfer intermediate adhesive layer is formed on and successively along the transfer face on which the fluorescent ink layer is formed.
In the fluorescent latent image transfer film, the total area of the formed yellow, magenta, cyan thermal sublimation dye layers, which is formed successively along the transfer face, is smaller than the total area, on/above the same substrate film, of layers selected from at least one of the thermal sublimation black layer, the heat-meting black ink layer, the fluorescent ink layer, the protective layer, and the thermal transfer intermediate adhesive layer.
In order to attain the above-mentioned objects, in the present invention there is provided a fluorescent latent image transfer method comprising the steps of putting, onto a transfer receiving material, a fluorescent latent image transfer film wherein a fluorescent ink layer formed of a resin binder comprising a fluorescent agent represented by the following formula (1) is deposited on/above a heat-resistant substrate film; heating the resultant in any pattern from the heat-resistant substrate film side of the fluorescent latent image transfer film by means of a heating element to transfer the fluorescent ink layer of the fluorescent latent image transfer film, correspondingly to the pattern of the heating element, onto the transfer receiving material, thereby forming a fluorescent latent image composed of the fluorescent agent on the transfer receiving material. 
wherein R1 is 
(n is a positive integer),
and R2 and R3 each represents H or an alkyl group.
In the fluorescent latent image transfer method, the fluorescent latent image is formed after an image composed of a visible ink is formed on the surface of the transfer receiving material.
In the fluorescent latent image transfer, an image composed of a visible ink is formed after the fluorescent latent image is formed on the surface of the transfer receiving material.
In the fluorescent latent image transfer method, preferably, the fluorescent latent image is formed in the middle of forming an image composed of a visible ink on the surface of the transfer receiving material.
In the fluorescent latent image transfer method, preferably, a protective layer is formed on the topmost surface of the transfer receiving material.
In the fluorescent latent image transfer method, in which the fluorescent latent image is formed after an image composed of a visible ink is formed on the surface of the transfer receiving material, preferably, a protective layer is formed after the visible image composed of the visible ink is formed, and the fluorescent latent image is formed on the surface of the protective layer.
In the fluorescent latent image transfer method, preferably, there is used a fluorescent ink layer integrated film wherein one or more layers selected from at least one of yellow, magenta, cyan and black thermal sublimation dye layers, a heat fusible black ink layer and the protective layer are formed on and successively along a transfer face on which the fluorescent ink layer is formed, so as to form the fluorescent latent image, the image composed of the visible ink, the protective layer and the like successively.
In the fluorescent latent image transfer method, preferably, a hologram pattern is formed in the protective layer, and the transfer receiving material is a card, a passport, or a license.
In the present invention, there is also provided a printed matter having a fluorescent latent image formed by the above-mentioned fluorescent latent image transfer method.
In order to attain the above-mentioned objects, in the present invention, there is provided a security pattern formed matter, which is a printed matter wherein a receptor layer on which information is recorded and a security pattern formed of a fluorescent latent image are at least formed on a surface of a transfer receiving material,
the security pattern being composed of a fluorescent material layer and an ultraviolet ray absorption pattern deposited into a pattern form on/above the fluorescent material layer, and an intermediate transfer medium wherein the receptor layer, the ultraviolet ray absorption pattern, and the fluorescent material layer are formed as a transfer layer being used so that the transfer layer of the intermediate transfer medium is transferred onto the surface of the transfer receiving material.
In the security pattern formed matter, preferably, the ultraviolet ray absorption pattern is formed by using an ultraviolet ray absorber transfer film having an ultraviolet ray absorber layer, and heating the transfer film in any pattern by means of a heating element to transfer the ultraviolet ray absorber layer correspondingly to the pattern of the heating means.
In the security pattern formed matter, preferably, the fluorescent material layer is a layer formed by using a fluorescent latent image transfer film having a fluorescent ink layer composed of a resin binder comprising a fluorescent agent.
In order to attain the above-mentioned objects, in the present invention there is provided a method for forming a security pattern formed matter, comprising the steps of using an intermediate transfer medium wherein a transfer layer comprising a fluorescent latent image composed of an ultraviolet ray absorption pattern and a fluorescent material layer, and a receptor layer on which information is recorded is formed on a substrate film, so as to transfer the transfer layer of the intermediate transfer medium on a transfer receiving medium, thereby forming a security pattern,
the intermediate transfer medium being a medium wherein the fluorescent latent image is formed in the manner that the ultraviolet ray pattern in the transfer layer after the transfer is positioned on/above the fluorescent ink layer.
In the present invention, there is also provided a dye transfer film, which is a thermal transfer medium wherein a dye layer and an adhesive layer are formed on and successively along a surface of a substrate film, the adhesive layer comprising a fluorescent material.
The xe2x80x9cimagexe2x80x9d referred to in the present invention means all of matters that can be recorded as information, for example, an image having continues gradation, such as a photograph, and monochromic or full color printed characters having no gradiation, symbols, pattern or the like. The fluorescent latent image transferred from the fluorescent ink layer and formed is an image that cannot be seen through usual visible rays but can be seen by absorbing ultraviolet rays when the image is irradiated with the ultraviolet rays. In order to prevent printed matters from being forged or copied, a secret code or an image which can be used for identification may be used. Specific examples thereof include a printed photograph having gradation, and characters, illustrations and abstract patterns having no gradation. An image composed of a visible ink, which is different from the fluorescent latent image and may be referred to as a visible image, means an image which is formed by a common printing or transferring method and can be seen with eyes under usual conditions.
The fluorescent latent image transfer film according to the present invention has the fluorescent ink layer. Thus, if the fluorescent latent image transfer film is put on a transfer receiving material and then the fluorescent ink layer is heated with a head of a thermal printer or the like, only the fluorescent agent of the fluorescent ink layer is transferred to the surface of the transfer receiving material so that a fluorescent image having continuous gradation can be formed. This fluorescent image cannot be seen through visible rays, but can be clearly recognized when being irradiated with ultraviolet rays. Therefore, by using this image, it can be judged whether or not the transfer receiving material is true. As a result, it is possible to prevent forgery or falsification, such as copy of the transfer receiving material, satisfactorily.
The fluorescent latent image transfer film of the present invention has the fluorescent agent comprising the resin binder containing the above-mentioned specific fluorescent compound. Therefore, the film is excellent in transferability and the gradiation-property of a fluorescent latent image.
The fluorescent latent image transfer method of the present invention is a method of using the fluorescent latent image transfer film having the fluorescent ink layer containing the specific fluorescent agent to perform transfer. Therefore, it is possible to form a fluorescent latent image having continues gradation satisfactory. This fluorescent image cannot be seen through visible rays, but can be clearly recognized when being irradiated with ultraviolet rays. According to the printed matter of the present invention, therefore, by using this fluorescent image, it can be judged whether or not the printed matter is true. As a result, it is possible to prevent forgery or falsification, such as copy of the printed matter, satisfactorily. The fluorescent ink comprising the resin binder containing the above-mentioned specific fluorescent agent is excellent in transferability and the gradiation-property of a fluorescent latent image.
According to the security pattern formed matter of the present invention, it is possible to obtain sufficient brightness of a fluorescent latent image pattern, and recognize easily the fluorescent image without having a bad influence on the raw material during printing process.